audioInputDevices: <span id="audioInputDevices"></span><hr>
audioOutputDevices: <span id="audioOutputDevices"></span><hr>
videoInputDevices: <span id="videoInputDevices"></span>

<script src="https://www.webrtc-experiment.com/DetectRTC/dev/CheckDeviceSupport.js"> </script>
<script type="text/javascript">
    checkDeviceSupport(function() {
        document.getElementById('audioInputDevices').innerHTML = audioInputDevices.length;
        document.getElementById('audioOutputDevices').innerHTML = audioOutputDevices.length;
        document.getElementById('videoInputDevices').innerHTML = videoInputDevices.length;
    });
</script>